Originally Posted by TMF Lindbeck
I would think 3" in from the collectors with 2 1/2 outs to keep the exhaust velocity up. The exhaust will cool and slow down through the cats and the 2 1/2 will help with the scavaging. Then again cats and hi performance don't really go hand in hand. IIRC h pipe for low end tq and the x pipe is best suited for hi rpm hp. Additionally the H or X pipe ideally would be as close as possible to the headers.
Thanks - so how about 3" cats at the headers, 3 to 2-1/2" reducers directly after the cats followed by an H pipe? Or should the H pipe be before the Cats? My understanding is that the Cats be as close to the heat source as possible to keep them from going bad (??)
I must run cats to be compliant I'm afraid